CN104395906A - Symmetry of discovered geometric relationships in a three dimensional model - Google Patents

Abstract

Systems and methods for identifying symmetric relationships in a product data management (PDM) system. The method includes receiving (505) a 3D model comprising a plurality of components and identifying (515) a plurality of target components (cl, c2, c3, c4, c5) from the plurality of components. The method includes identifying (515) a plane of symmetry (pi, p2) in the 3D model and determining (520) a position of each target component relative to the plane of symmetry. The method includes adding ( 525 ) target components to corresponding groups according to the determined positions, and creating ( 530 ) an equivalence class ( sa1 , sd1 ) for each target component group. The method includes storing (535) symmetric relationships between the created equivalence classes.

Description

Symmetry of discovered geometric relationships in 3D models

The invention relates to a method of identifying symmetric relationships, a product data management data processing system and a computer readable medium according to the independent claims.

technical field

The present disclosure generally relates to computer-aided design, visualization and manufacturing systems, product lifecycle management (“PLM”) systems, and similar systems (collectively referred to as “product data management” systems or “PDM”) for managing product data and other items. system).

Background technique

The PDM system manages PLM and other data. An improved system is expected.

Contents of the invention

Various disclosed embodiments include systems and methods for improved PDM processing, including systems and methods for managing symmetry within discovered geometric relationships in a three-dimensional model in a product data management (PDM) system. method. The method includes receiving a 3D model including a plurality of components and identifying a plurality of target components from the plurality of components. The method includes identifying a plane of symmetry in the 3D model and determining the position of each target component relative to the plane of symmetry. The method includes adding target components to corresponding groups based on the determined positions and creating an equivalence class for each target component group. The method includes storing the symmetric relations between the created equivalence classes.

The foregoing has outlined rather broadly the features and technical advantages of the present disclosure so that those skilled in the art may better understand the following detailed description. Additional aspects and advantages of the disclosure will be described hereinafter which form the subject of the claims. Those skilled in the art should appreciate that they may readily use the conception and specific embodiment disclosed as a basis for modifying or designing other structures for carrying out the same purposes of the present disclosure. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the disclosure in its broadest form.

Before beginning the following detailed description, it may be beneficial to set forth definitions of certain words or phrases used throughout this patent document: the words "include" and "comprise" and their derivatives mean inclusion without limitation; The term "or" is inclusive, referring to and/or; the phrases "associated with" and "associated with" and their derivatives may mean to include, to be included, to be interconnected with, to comprise, to be included, to connect to or connected to, coupled to or coupled to, capable of communicating with, cooperating with, interleaved with, juxtaposed with, proximate to, bound to or bound to, having, or having properties thereof, etc.; and the term "controller" refers to Any device, system, or portion thereof that controls at least one operation, whether such device is implemented by hardware, firmware, software, or a combination of at least two of the above. It should be noted that the functionality associated with any particular controller, whether locally or remotely, may be centralized or distributed. Definitions for certain words and phrases are provided throughout this patent document, and those skilled in the art should understand that such definitions apply to many, if not most, instances prior to and including such defined words and phrases. future use. While some words may encompass a wide variety of embodiments, the appended claims may expressly limit these words to specific embodiments.

Description of drawings

For a fuller understanding of the present disclosure and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, in which like reference numerals refer to like objects, in which:

Figure 1 depicts a block diagram of a data processing system capable of implementing embodiments;

2A and 2B illustrate examples of symmetric entities according to disclosed embodiments;

Figure 3A shows a simple example representation of a model for illustrating symmetric relationships according to disclosed embodiments, and Figures 3B and 3C show geometric relationship diagrams corresponding to Figure 3A, according to disclosed embodiments;

Figure 4A shows an example of a model in which a first equivalent class has three members and a second equivalent class includes only two members according to disclosed embodiments, and Figure 4B shows the corresponding The geometric relationship diagram;

Figure 5 depicts a flow diagram of processing in accordance with disclosed embodiments;

Figure 6 shows an example of a target component in a model according to disclosed embodiments;

FIG. 7 illustrates the use of optional constraints when a component is moved and the optional constraints are maintained, according to disclosed embodiments;

Figure 8 illustrates the use of optional constraints when a component rotates the component's axis;

Figure 9 illustrates an example of segmentation by multiple planes of symmetry in accordance with disclosed embodiments;

Figure 10A shows an example of a single plane of symmetry according to a disclosed embodiment, Figure 10B shows a corresponding sense according to a disclosed embodiment, and Figure 10C shows a sense according to a disclosed embodiment the corresponding relationship diagram; and

FIG. 11A shows an example of two planes of symmetry according to disclosed embodiments, FIG. 11B shows corresponding orientations according to disclosed embodiments, and FIG. 11C shows corresponding orientations according to disclosed embodiments. relation chart.

Detailed ways

1 through 11 , discussed below, and the various embodiments used to describe the principles of the disclosure in this patent document are by way of illustration only and should not be construed in any way to limit the scope of the disclosure. Those skilled in the art will understand that the principles of the present disclosure may be implemented in any suitably configured device. The many innovative teachings of the present application will be described with reference to exemplary, non-limiting embodiments.

Geometric relationship recognition enables users to edit models, even non-native or imported models, while preserving important design features.

Given any three-dimensional (3D) CAD model, there are many geometric relationships that a user may wish to preserve when editing. For example, a user may wish to maintain a certain distance between two features for features that are to be "mirrored" or symmetrical about an arbitrary line or plane; features that are to be kept parallel, or other features. When such a relationship is found in the model, it may be necessary to specifically consider symmetric relationships. The disclosed embodiments include systems and methods for processing discovered symmetric relationships.

Figure 1 depicts a block diagram of a data processing system capable of implementing an embodiment, such as a PDM system or a clearing system configured, inter alia, by software or otherwise, to perform processing as described herein, and in particular as described herein Each of a plurality of interconnection and communication systems. The depicted data processing system includes processor 102 coupled to L2 cache/bridge 104 , which in turn is coupled to local system bus 106 . Local system bus 106 may be, for example, a Peripheral Component Interconnect (PCI) fabric bus. Also connected to the local system bus in the depicted example are main memory 108 and graphics adapter 110 . Graphics adapter 110 may be connected with display 111 .

Other peripheral devices such as a local area network (LAN)/wide area network/wireless (eg, WiFi) adapter 112 may also be connected to the local system bus 106 . Expansion bus interface 114 connects local system bus 106 with input/output (I/O) bus 116 . I/O bus 116 connects with keyboard/mouse adapter 118 , disk controller 120 and I/O adapter 122 . Disk controller 120 may be coupled to storage device 126, which may be any suitable machine-usable or machine-readable storage medium, including but not limited to: non-volatile, hard-coded type media such as read-only memory (ROM) or Erasable, electrically programmable read-only memory (EEPROM), magnetic tape storage devices, and user-recordable media such as floppy disks, hard disk drives, and compact disk read-only memory (CD-ROM) or digital versatile disks (DVD) and other known optical, electrical or magnetic storage devices.

Also connected to the I/O bus 116 in the example shown is an audio adapter 124 to which a speaker (not shown) may be connected to play sound. Keyboard/mouse adapter 118 provides connection for a pointing device (not shown) such as a mouse, trackball, track pointer.

Those of ordinary skill in the art should understand that the hardware depicted in FIG. 1 may vary due to specific implementations. For example, other peripheral devices, such as optical disc drives, etc., could be used in addition to or instead of the depicted hardware. The depicted examples are provided for illustration purposes only, and are not meant to imply architectural limitations with respect to the present disclosure.

A data processing system according to an embodiment of the present disclosure includes an operating system employing a graphical user interface. The operating system allows multiple display windows to be simultaneously presented in the graphical user interface, where each display window provides an interface to a different application or a different instance of the same application. Users can operate the cursor in the GUI through a pointing device. The position of the cursor can be changed and/or events such as mouse button clicks can be generated to drive the desired response.

One of various commercial operating systems, suitably modified, such as a version of Microsoft Windows ^(TM) , a product of Microsoft Corporation of Redmond, Washington, may be used. The operating system is modified or created according to the present disclosure as described.

LAN/WAN/wireless adapter 112 may be connected to network 130 (not part of data processing system 100), which may be any public or private data processing system network or combination of such networks as known to those skilled in the art, Including the Internet. Data processing system 100 may be in communication with server system 140 via network 130 , but may also be implemented as, for example, a separate data processing system 100 which is also not part of data processing system 100 .

The mathematical definition of an equivalence class ("EC") as used herein is a group of members that share an equivalence relationship. Equivalence relations are reflexive, symmetric and transitive. Equivalence classes have the following useful property: elements can only be members of one equivalence class qualified by a particular equivalence relation.

Equivalence classes can thus be used to define geometric relations in a CAD model where those relations are equivalence relations.

Equivalence relations exist in models where geometric shapes share at least one equivalence component; the components of equivalence relations are centers, axes, planes, directions, radii, minor radii, or half angles.

The following equivalence relations are useful in geometric modeling in accordance with the disclosed techniques:

• Identical (I): Geometric shapes share the same type and all components.

• Concentric (SC): Geometric shapes share the same central component.

● Concentric (SA): Geometries share the same axis components.

● Same Plane (SP): Geometric shapes share the same planar component.

• Same Shape (SS): Geometric shapes share the same type of components and the same radius, large and small radii, or half-width components.

● Same Direction (SD): Geometric shapes sharing the same direction component, are aligned or anti-aligned.

From these equivalence relations, classes can be formed that include geometric shapes that share the same equivalence relations.

Many models are constructed with symmetry across a given plane, and it is desirable to discover and preserve these symmetries when editing these models. Symmetric entities in a model are often also part of other geometrically valid conditions that are discovered at the same time as the symmetry. Often enforcing these additional conditions limits the edits a user can make.

2A and 2B illustrate examples of symmetric entities. In FIG. 2A , the surface 202 of the cylinder c1 is bilaterally symmetrical to the surface 204 of the cylinder c2 via the plane P1206 . Both cylinder c1 and cylinder c2 are also geometrically equivalent. Keeping c1 202 equal to c2 204 does not cause c1 202 to be rotated as shown in Figure 2B.

There is a hierarchy between these equivalence classes, as listed above, with equivalence being the lowest, then concentric, coaxial, coplanar, and isomorphic and finally isotropic at the top.

In various implementations, a hierarchy between equivalence classes may have one or more of the following characteristics:

• Relationships defined in lower-level classes imply higher-level class relationships, but these relationships are not expressly represented. For example, two planes that are identical are also coplanar and in the same direction.

• A directed edge from node A to node B can be interpreted as "B is a member of A" or "A is a parent of B".

• The terminal nodes of the graph (ie, members of the equivalent class) consist of model geometries.

• Each terminal node must belong to one and only one peer node.

• Each class node can belong to multiple equivalence classes with different types, but each class node can only belong to one class of a certain type.

The product assembly may include multiple basic 3D components, each of which may share various equivalence relationships. Each of these assemblies can be represented by a connection diagram showing the equivalence relationship between each component type.

In cases where symmetric conditions are requested to be preserved and these symmetric conditions exist in the model, symmetric relationships are preferred over other relationships. The preference for symmetry is applied to all relational conditions found in the model. Because symmetric components generally do not have equivalence, eg, symmetric components may not be in the same orientation, the symmetric relationships described herein are not part of the equivalence class hierarchy described above.

The mathematical concept of equivalence classes is used to discover and store geometric relations to represent equivalent geometric relations in the model. A non-equivalence relationship is then formed between these classes. This representation ensures a complete and compact representation and also enables efficient discovery.

Figure 3A shows a simple example representation of a model used to illustrate the symmetric relationship, and Figures 3B and 3C show a geometric relationship diagram corresponding to Figure 3A.

Figure 3A shows cylinders c1, c2, c3 and c4, two on each side of plane P1. Fig. 3B shows a relationship graph indicating that cl, c2, c3 and c4 are part of the same equivalent class i1, the same coaxial class sa1 and the same symetrical class sd1. Figure 3B shows a relationship graph with equivalence class discovery turned on and symmetric relation discovery turned off.

As can be seen from Figure 3A, if symmetry across the plane P1 is to be preserved when rotating one of the cylinder axes, the equivalence class i1 must be split into two classes, one of which includes c1 and c2 and the other includes c3 and c4. That is, if one cylinder shaft is rotated, at least the corresponding/opposite cylinder shaft on the other side of plane P1 must also be rotated in the opposite direction. Assuming that c1 and c2 remain equal, and c3 and c4 remain equal, the equality class i1 shown in Figure 3B must be split into two equality classes i1 and i2 as shown in Figure 3C.

This division must also be generalized to coaxial and isotropic classes above i1/i2 to yield the structure shown in Figure 3C, where symmetry Sym1 is then applied between two equivalent classes. FIG. 3B shows a relationship diagram when both the discovery of equivalence classes and the discovery of symmetric relations are turned on.

This splitting of the complete class hierarchy enables the user to move or rotate any of these cylinders and the system modifies/moves and displays the other faces accordingly.

Many classes will not include a completely symmetrical set of members. Fig. 4A shows an example of a model in which, as shown in the geometry diagram of Fig. 4B, the equivalence class i1 has three members and the equivalence class i2 includes only two members.

In this case, the structure is still split by the plane of symmetry P1, but not evenly as in the first example, but so that the cylinders c0, c1 and c2 are part of the same class i1, and the cylinder c3 and c4 are part of the equivalence class i2. The symmetry relation is shown as Sym1:P1, denoting symmetry relation 1 about the symmetry plane P1.

This article refers to this process of splitting classes in a structure as "splitting". Splitting can be triggered by examining all members of a relationship to determine if any two members are symmetric. If there is symmetry between any two members, the class can be split using the processing described below.

FIG. 5 depicts a flowchart of a process in accordance with disclosed embodiments, and the flowchart of this process is described below with respect to other illustrative figures.

The system receives the model (step 505). The "system" may be a PDM data processing system as described herein, and the model is a 3D model comprising a plurality of components. As used herein, "receiving" may include loading from a storage device, receiving from another device or process, or receiving via interaction with a user. The model includes the geometry and parameters of each component that enable the characteristics of the components to be compared against the geometric relationships described herein.

The system may identify a number of target components to be checked for symmetry (step 510). This step may be performed in response to user input such as a command to find symmetric components, and may be performed for all members of a relationship class as described herein. This step can include receiving or creating a relationship diagram that includes the target components.

Figure 6 shows an example of target components in the model.

The system can identify planes of symmetry in the model (step 515). This step may be performed automatically by the system, or this step may include receiving a user selection of a plane of symmetry. Figure 6 shows the plane of symmetry S and several cylindrical surfaces C1 to C5.

The system may determine for each target component which side of the plane of symmetry the target is on (step 520). Any process for assigning sides of components may be used, such as, but not limited to, using bounding box centers or centroids, using color or other engineering or design attributes, or using other means. A target component may be, for example, a single model face when splitting a homogeneous class, or a collection of model faces when splitting a high-level class coaxial or unidirectional, or others.

Each target component is identified by its position with respect to the plane of symmetry, including components determined to be located in front of the plane of symmetry; components determined to be located behind the plane of symmetry; and components determined to be located on the plane of symmetry. Of course, "in front" or "in rear" are relative terms and are intended to include equivalent determinations about "left" and "right", "upper" and "lower" or others. For example, in FIG. 6, the cylinder with cylindrical surfaces C1 and C2 is on the left of the plane of symmetry S, while the cylinder with cylindrical surfaces C4 and C5 is on the right of the plane of symmetry S.

The system adds each target component to the group according to the identified location (step 525). If there are remaining target components, the process may loop to step 520 . For example, a cylinder with cylindrical faces C1 and C2 may be placed in a first group, and a cylinder with cylindrical faces C4 and C5 may be placed in a second group. The respective groups include those target components on either side of the symmetry plane.

The system creates an equivalence class for each non-empty group (step 530). Classes can be created for the first group as well as for the second group. This step may include placing the new class in the diagram.

The system creates a symmetric relationship between the two groups that includes symmetric components (step 530). The system can create a symmetrical relationship between the first group and the second group.

The system stores the symmetric relationship (step 535). This step may include storing the symmetric relationship with the relationship graph and may include storing the modified relationship graph.

In some implementations, finding and processing the symmetry in the equivalent class first serves as a trigger for repeating the process in higher-level classes without having to rediscover the symmetry.

As mentioned in the treatment above, in some models the segmentation may conclude that members are neither on one side nor on the other of the symmetry plane, which is referred to in this paper as "self-symmetry" . Fig. 6 shows five cylindrical faces C1, ..., C5 that would be part of an equivalence class; the cylinder with cylindrical face C3 is self-symmetrical and can be placed in a third group.

This third set of faces can be treated differently (in the example of FIG. 6 the third set only includes a single face C3). Instead of being constrained to maintain symmetry while moving, different sets of constraints can be imposed depending on the type of surface involved. In this example, the following constraints are imposed, but of course other implementations may use others:

• The cylinder with cylindrical face C3 is constrained to remain parallel to the plane of symmetry.

● The cylinder with cylindrical face C3 imposes two optional constraints, one of which is used to maintain consistency with the equivalent class including cylinders with cylindrical faces C1 and C2, and the other constraint is used to maintain consistency with the same class including cylinders with cylindrical faces C1 and C2 The equivalence of the cylinders of C4 and C5 is the same. Optional indicates that the constraint cannot conflict with the movement requested by the user or with other constraints on the model.

In some implementations, for example, the system can impose constraints to keep the central geometry self-symmetric about a plane of symmetry. In the case of a cylinder, for example, the constraint could be that the cylinder axis is parallel to the symmetry plane normal. For planes, the constraint can be that the plane normal is perpendicular to the symmetry plane normal. Optional constraints can then be used to try to keep the central geometry on either side equal to the equivalent class.

Figure 7 illustrates the use of the optional constraint when moving up the cylinder with cylindrical face C4 and maintaining the optional constraint, using the same elements as in Figure 6 . When the cylinder with cylinder face C4 is moved up, the cylinder with cylinder face C5 as part of the second equivalent class/group is also moved up, and the cylinders with cylinder faces C1 and C2 as part of the second equivalent class/group A part of the first equivalent class/group of group symmetry is also moved up, and the cylinder with cylindrical face C3 is moved up according to the above optional constraints.

Figure 8 shows the use of optional constraints when the cylinder with cylindrical face C4 rotates its axis, using the same elements as in Figure 6 . When the cylinder with cylindrical face C4 is rotated, the cylinder with cylindrical face C5 as part of the second equivalent class/group is also rotated, and the cylinders with cylindrical faces C1 and C2 as symmetric with the second equivalent class/group A part of the first equivalent class/group of is rotated in the opposite direction, and the cylinder with cylindrical surface C3 remains stationary according to the optional constraints above.

The segmentation process described above can also be used to process multiple symmetry planes.

FIG. 9 shows an example of division by a plurality of symmetry planes P1 and P2. In this example, the cylinders with symmetry planes C1 , C2 , C3 and C4 are all parallel and have no symmetry, and they can all be members of a single coaxial class (via two coaxial classes and two equivalent classes).

However, to allow rotation of the axis of C1, this isotropic class needs to be split into four groups/classes and a proper symmetric relationship needs to be imposed.

To achieve the above, the system can assign a "sense" about each symmetry plane to each component of the class to form a "signature". All members with the same sign difference then form a single split. The orientation is defined according to which side of the plane the partitioning scheme determines the component to be on. The front of the plane is defined as the positive direction, and the rear of the plane is defined as the negative direction. In the case of the above processing, the target components are grouped according to the respective sign differences defined by the pointing of each target component.

FIG. 10A shows an example of a single plane of symmetry P1 for cylinders c0 to c4. FIG. 10B shows the corresponding orientations for these cylinders c0 to c4 and their faces and planes, and FIG. 10C shows the corresponding relationship diagram.

In this example, c1 is symmetrical to c4, c2 is symmetrical to c3, and all five cylinders are equal. As shown in FIG. 10B, faces c0, c1, and c2 have the same orientation, and faces c3 and c4 have the same orientation. Thus, as shown in FIG. 10C , the group of equivalent geometric shapes is split into two groups, and two equivalence classes i1 and i2 are created, and a symmetry relation Sym1 is created between the equivalence classes.

FIG. 11A shows an example of two symmetry planes P1 and P2 of the above cylindrical surfaces c1 to c4 corresponding to FIG. 9 . Figure 11B shows the corresponding orientations for these cylinders and their faces and planes, and Figure 11C shows the corresponding relationship diagram.

In this example, the cylinder is symmetrical about two different planes of symmetry P1 and P2. When considering orientations with respect to two planes, as shown in Figure 1 IB, all four cylinders have different sign differences (defined by the combination of orientations). Thus, as shown in the relationship diagram of Figure 11C, four separate classes of equivalence, coaxial, and isotropic are created.

Of course, those skilled in the art will appreciate that certain steps in the above-described processes may be omitted, performed simultaneously or sequentially, or performed in a different order unless specifically indicated or required by the order of operations. The steps and operations of various processes may be combined in various implementations.

Those skilled in the art will appreciate that for simplicity and clarity, the full structure and operation of all data processing systems suitable for use with the present disclosure have not been depicted or described herein. Instead, only those portions of a data processing system that are characteristic of the present disclosure or necessary for an understanding of the present disclosure are depicted and described. The remainder of the construction and operation of data processing system 100 may follow any of various current implementations and practices known in the art.

It is important to note that although the present disclosure includes descriptions in the context of fully functional systems, those skilled in the art will appreciate that at least some of the mechanisms of the present disclosure can be embodied in various forms of machine-usable, computer-usable or computer-readable media, and this disclosure applies equally regardless of the specific type of instruction or signal bearing media or storage media by which the distribution is actually performed. Examples of machine-usable/readable or computer-usable/readable media include: non-volatile, hard-coded type media such as read-only memory (ROM) or erasable, electrically programmable read-only memory (EEPROM), and user-programmable Recording type media such as floppy disks, hard disk drives, and compact disk read-only memories (CD-ROMs) or digital versatile disks (DVDs).

Although the exemplary embodiments of the present disclosure have been described in detail, those skilled in the art will appreciate that various modifications can be made to the present disclosure without departing from the spirit and scope of the disclosure in its broadest form. Changes, Substitutions, Modifications and Improvements.

Nothing in the description in the present application should be read as implying that any particular element, step, or function is an essential element that must be included in the scope of the claims, and the scope of patented subject matter is defined only by the issued claims.

List of reference symbols used, glossary

100 data processing system

102 processors

104 Cache/Bridge

106 local system bus

108 main memory

110 graphics adapter

111 display

112 LAN/WAN/Wireless Adapter

114 Expansion bus interface

116 input/output bus, I/O bus

118 keyboard/mouse adapter

120 disk controller

122 I/O Adapter

124 audio adapter

126 storage devices

130 network

140 server system

200 working parts

202 model cylindrical surface

204 model cylindrical surface

206 Plane P1

505 Receive Model

510 Identify target components

515 Identify Symmetry Plane

520 Determine the position of the target relative to the plane

525 Add target to group based on location

530 Create an equivalence class for each non-empty group

535 Store symmetric relations

C1 cylindrical surface

C2 cylindrical surface

C3 cylindrical surface

C4 cylindrical surface

C5 cylindrical surface

c0 cylinder

c1 cylinder

c2 cylinder

c3 cylinder

c4 cylinder

c5 cylinder

I equivalent

i1 class, equal class

i2 class, equivalent class

P1 plane, symmetry plane

P2 plane, symmetry plane

S Symmetry plane

SA coaxial

SC Concentric

SD same direction

SP same plane

SS isomorphic

sa1 coaxial

sd1 same direction class sd1

Sym1 Symmetry

Sym1:P1 symmetric relationship

ASIC application specific integrated circuit

CAD computer aided design

I/O input/output

LAN local area network

PCI Peripheral Component Interconnect

PDM Product Data Management

PLM Product Lifecycle Management

WAN wide area network

Claims (20)

1. A method for identifying symmetric relationships comprising: receiving (505) a 3D model comprising a plurality of components in a product data management system (100), hereinafter denoted by the PDM system (100); identifying (510) a plurality of target components (c1, c2, c3, c4, c5) from the plurality of components; identifying (515) a plane of symmetry (p1, p2) in said 3D model; determining (520) the position of each of said target components relative to said plane of symmetry (p1, p2); adding (525) said target component to a corresponding set (sa1, sd1) according to the determined position; creating (530) an equivalence class (sa1, sd1) for each target component group; and The symmetric relationship between the created equivalence classes (sa1, sd1) is stored (535). 2. The method of claim 1, wherein the symmetric relationship is stored in a geometric relationship graph. 3. A method according to claim 1 or 2, wherein said respective group comprises said target components (c3) located on either side of said plane of symmetry (p1, p2). 4. The method as claimed in one of claims 1 to 3, wherein the created equivalence classes (sa1, sd1) are stored in a geometric diagram. 5. The method according to one of claims 1 , 2 or 4, wherein said PDM system (100) also targets components (c1 , c2, c4, c5) are identified and the target is added to the third group. 6. The method according to one of claims 1 to 5, wherein the PDM system (100) assigns each target component an orientation with respect to one or more symmetry planes (p1, p2). 7. The method according to claim 6, wherein said target components (c1, c2, c3, c4, c5) for grouping. 8. A product data management system (100), said product data management system (100) is represented by a PDM system (100) below, which includes: at least one processor (102); and memory (108, 126) accessible, the PDM system (100) configured to: receiving (505) a 3D model comprising a plurality of components; identifying (510) a plurality of target components (c1, c2, c3, c4, c5) from the plurality of components; identifying (515) a plane of symmetry (p1, p2) in said 3D model; determining (520) the position of each of said target components (c1, c2, c3, c4, c5) relative to said plane of symmetry (p1, p2); adding (525) said target component to a corresponding group according to the determined position; creating (530) an equivalence class (sa1, sd1) for each target component group; and The symmetric relations between the created equivalence classes are stored (535). 9. The PDM system (100) according to claim 8, wherein the symmetric relationship is stored as a geometric relationship graph. 10. The PDM system (100) according to claim 8 or 9, wherein said respective group comprises said target components (c3) located on either side of said plane of symmetry (pl, p2). 11. The PDM system according to one of claims 8 to 10, wherein the created equivalence classes (sa1, sd1) are stored as geometric relationship diagrams. 12. The PDM system (100) according to one of claims 8, 9 or 11, wherein the PDM system (100) also treats the The target component (cl, c2, c4, c5) is identified and the target is added to the third group. 13. The PDM system (100) according to one of claims 8 to 12, wherein the PDM system (100) assigns each target component an orientation with respect to one or more planes of symmetry. 14. The PDM system (100) according to claim 13, wherein said target components (c1, c2, c3, c4, c5) are selected according to respective sign differences defined by said pointing of each target component grouping. 15. A non-transitory computer-readable medium encoded with computer-executable instructions which, when executed, cause the following product data management system (100), denoted by a PDM system (100): receiving (505) a 3D model comprising a plurality of components; identifying (510) a plurality of target components (c1, c2, c3, c4, c5) from the plurality of components; identifying (515) a plane of symmetry (p1, p2) in said 3D model; determining (520) the position of each of said target components (c1, c2, c3, c4, c5) relative to said plane of symmetry (p1, p2); adding (525) said target component to a corresponding group according to the determined position; creating (530) an equivalence class (sa1, sd1) for each target component group; and The symmetric relationship between the created equivalence classes (sa1, sd1) is stored (535). 16. The computer readable medium of claim 15, wherein the symmetric relationship is stored as a geometric relationship graph. 17. Computer readable medium according to claim 15 or 16, wherein said respective group comprises said target component (c3) located on either side of said plane of symmetry (p1, p2). 18. The computer readable medium according to claim 15, wherein the created equivalence classes (sa1, sd1) are stored in a geometric relationship graph. 19. The computer-readable medium according to one of claims 15, 16 or 18, wherein the PDM system (100) also detects objects that are not on either side of the symmetry plane (p1, p2) Components (cl, c2, c4, c5) are identified and the object is added to the third group. 20. The computer-readable medium according to one of claims 15 to 19, wherein the PDM system (100) assigns each target component (c1, c2, c3, c4, c5) relative to one or more orientations of a plurality of symmetry planes, and wherein said target components are grouped according to respective sign differences defined by said orientation of each target component.